Read the plan service's today from the scheduler's clock

The plan service read "today" from time.Now, so the plan-draft schedule
tests could not pin the plan_ready title on the fake clock. NewService now
takes a clock; the server passes the scheduler's Now. The plan-draft tests
read the started scheduler's fake clock and assert each plan_ready row's
title and channel alongside the existing key assertions.

Maestro task ece60217-04d0-43a4-9690-4aba2a00d420

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/scheduler/scheduler.go

@@ -378,6 +378,11 @@ func (s *Scheduler) Wake() {
 	s.signal()
 }
 
+// Now is the time on the scheduler's clock, by which its schedules fire.
+func (s *Scheduler) Now() time.Time {
+	return s.now()
+}
+
 // signal leaves one token in wake for the loop.
 func (s *Scheduler) signal() {
 	select {